Organomercurial-volatilizing bacteria in the mercury-polluted sediment of Minamata Bay, Japan

A total of 4,604 bacterial strains isolated from the sediments of Minamata Bay and nearby low-level-mercury stations (control stations) were screened for the ability to volatilize mercury from inorganic and organic mercurial compounds. The strains that volatilize mercury from several kinds of organomercurials were found only in the sediments of Minamata Bay.     

Organomercurial-volatilizing bacteria in the mercury-polluted sediment of Minamata Bay, Japan.

A total of 4,604 bacterial strains isolated from the sediments of Minamata Bay and nearby low-level-mercury stations (control stations) were screened for the ability to volatilize mercury from inorganic and organic mercurial compounds. The strains that volatilize mercury from several kinds of organomercurials were found only in the sediments of Minamata Bay.     

Removal of mercury from mercury-contaminated sediments using a combined method of chemical leaching and volatilization of mercury by bacteria

A method for the removal of mercury sulfide frommercury-contaminated sediments was developed, whichconsists of chemical leaching and volatilization ofmercury by bacteria. More than 85% of the mercury insediment containing 0.11–37.4 mg/kg of mercury wasefficiently extracted with 3 M HCl and 74 mMFeCl₃. Subsequent volatilization by bacteriaresulted in the removal of 62.9–75.1% of mercury frommercury-contaminated Minamata Bay sediments. Methylmercury was also eliminated from soil at a highefficiency. Thus, this combined method of chemicaland microbial treatments could be used for efficientremoval of both organic and inorganic mercurials fromnatural sediments.     

Assessment of the contamination level of bottom sediments of Amursky Bay (Sea of Japan) and their potential toxicity

The contamination of surface bottom sediments of the Amursky Bay (the Sea of Japan) and their potential toxicity were assessed by the computation of contamination indexes and the ecological risk index, as well as by comparison of the concentrations of toxicants in the sediments with the sediment quality guidelines (SQD) values adopted by the US Environmental Protection Agency (EPA). It was shown that sediments from the coastal zone of Amursky Bay adjacent to the Vladivostok City were the most contaminated. The organochlorine pesticide DDT and such heavy metals as zinc, copper, and nickel were major inputs to the potential toxicity of the sediments. Linear regression analysis revealed positive, although not always significant, correlations between the ecological risk index and quotients characterizing the level of pathological changes in the gonads and the number of anomalies in the development of progeny of the sea urchin Strongylocentrotus intermedius. The obtained data array enables us to conclude that contamination of bottom sediments by heavy metals and DDT causes great risk for the reproduction of S. intermedius and other benthic invertebrates in the coastal part of Amursky Bay adjoining the city.     

Pollution in Peter the Great Bay, Sea of Japan, and its biological consequences

This review summarizes information published in the 1980s–1990s about anthropogenic pollution in Peter the Great Bay, the largest of the bays in the northwestern part of the Sea of Japan. The coastal zone of the bay occupies about 12% of the area of Primorskii Province and is the most heavily populated. The bulk of the human settlements, the seaports of Vladivostok and Nakhodka, railways, industrial enterprises, and developed agriculture are located in the coastal zone. Sewage waters containing multicomponent mixtures of polluting agents of both mineral and organic origin are discharged into the coastal waters of the bay. This paper presents information about the concentration of major classes of polluting agents (oil hydrocarbons, polychlorinated hydrocarbons, surfactants, heavy metals, and radionuclids) in the water and bottom sediments of the bay. The results of physico-chemical and biogeochemical investigations performed in the 1970s–1990s justify considering Zolotoi Rog Bay, Bosfor Vostochnyi Strait, Nakhodka Bay (especially its innermost portion, around the harbor of Nakhodka), and Amurskii Bay to be the most polluted areas in Peter the Great Bay. The information about the biological consequences of pollution in these water areas is briefly reviewed.     

Phytoremediation of Mercury- and Methylmercury-Polluted Soils Using Genetically Engineered Plants

Inorganic mercury in contaminated soils and sediments is relatively immobile, though biological and chemical processes can transform it to more toxic and bioavailable methylmercury. Methylmercury is neurotoxic to vertebrates and is biomagnified in animal tissues as it is passed from prey to predator. Traditional remediation strategies for mercury contaminated soils are expensive and site-destructive. As an alternative we propose the use of transgenic aquatic, salt marsh, and upland plants to remove available inorganic mercury and methylmercury from contaminated soils and sediments. Plants engineered with a modified bacterial mercuric reductase gene, merA, are capable of converting Hg(II) taken up by roots to the much less toxic Hg(0), which is volatilized from the plant. Plants engineered to express the bacterial organo-mercurial lyase gene, merB, are capable of converting methylmercury taken up by plant roots into sulfhydryl-bound Hg(II). Plants expressing both genes are capable of converting ionic mercury and methylmercury to volatile Hg(0) which is released into an enormous global atmospheric Hg(0) pool. To assess the phytoremediation capability of plants containing the merA gene, a variety of assays were carried out with the model plants Arabidopsis thaliana, and tobacco (Nicotiana tabacum).     

Integrated assessment of heavy metal contamination in sediments from a coastal industrial basin, NE China

The purpose of this study is to investigate the current status of metal pollution of the sediments from urban-stream, estuary and Jinzhou Bay of the coastal industrial city, NE China. Forty surface sediment samples from river, estuary and bay and one sediment core from Jinzhou bay were collected and analyzed for heavy metal concentrations of Cu, Zn, Pb, Cd, Ni and Mn. The data reveals that there was a remarkable change in the contents of heavy metals among the sampling sediments, and all the mean values of heavy metal concentration were higher than the national guideline values of marine sediment quality of China (GB 18668-2002). This is one of the most polluted of the world's impacted coastal systems. Both the correlation analyses and geostatistical analyses showed that Cu, Zn, Pb and Cd have a very similar spatial pattern and come from the industrial activities, and the concentration of Mn mainly caused by natural factors. The estuary is the most polluted area with extremely high potential ecological risk; however the contamination decreased with distance seaward of the river estuary. This study clearly highlights the urgent need to make great efforts to control the industrial emission and the exceptionally severe heavy metal pollution in the coastal area, and the immediate measures should be carried out to minimize the rate of contamination, and extent of future pollution problems.     

Structure analysis of a class II transposon encoding the mercury resistance of the Gram-positive Bacterium bacillus megaterium MB1, a strain isolated from minamata bay, Japan.

A unique transposon was found in the chromosome of Bacillus megaterium MB1, a Gram-positive bacterium isolated from mercury-polluted sediments of Minamata Bay, Japan. The transposon region of a 14.5kb DNA fragment was amplified by PCR using a single PCR primer designed from the nucleotide sequence of an inverted repeat of class II transposons. The molecular analysis revealed that the PCR-amplified DNA fragment encodes a transposition module similar to that of Tn21. The transposon also encodes a broad-spectrum mercury resistance region having a restriction endonuclease map identical to that of Bacillus cereus RC607, a strain isolated from Boston Harbor, USA. The result of a phylogenetic analysis of the amino acid sequence of putative resolvase of the transposon showed that the transposon is phylogenetically closer to the transposons of Gram-positive bacteria than those of Gram-negative bacteria. Besides the transposition module and mer operon, the transposon encodes a mobile genetic element of bacterial group II introns between the resolvase gene and mer operon. The intron, however, does not intervene in any exon gene. The discovery of this newly found combination of the complex mobile elements may offer a clue to understanding the horizontal dissemination of broad-spectrum mercury resistance among microbes.     

Heavy metals contamination and accumulation in submerged macrophytes in an urban river in China

Deteriorating urban water quality has attracted considerable attention in China. We investigated the contamination levels and distribution of heavy metals (As, Cd, Cu, Ni, Pb, and Zn) in Yuxi River water and sediments, and assessed the heavy metal accumulation capability of five species of submerged macrophytes: Vallisneria natans (Lour.) Hara, Potamogeton pectinatus L., Hydrilla verticillata (L. f.) Royle, Myriophyllum spicatum L., and Potamogeton crispus L. Samples were collected from upstream and downstream locations in different season. The results showed that the levels of heavy metals in the downstream areas were higher than in the upstream areas. Heavy metal concentrations in the river water during the dry seasons were higher than those during the rainy seasons, and the opposite results appeared in sediments and submerged macrophytes. In general, the river was slightly contaminated by heavy metals, and the concentrations of Pb and Ni in this river should serve as a warning, while Cd and Zn pollution in the sediments desperately needs to be removed. Furthermore, Potamogeton pectinatus L. showed a higher accumulation capacity for these metals among the five native submerged macrophytes and could be defined as a hyperaccumulator for Cd. Therefore, the potential use of native aquatic plants in contaminated rivers is worth further exploration.     

Heterogeneous distribution in sediments and dispersal in waters of Alexandrium minutum in a semi-enclosed coastal ecosystem

Within the framework of research aimed at using genetic methods to evaluate harmful species distribution and their impact on coastal ecosystems, a portion of the ITS1rDNA of Alexandrium minutum was amplified by real-time PCR from DNA extracts of superficial (1–3 cm) sediments of 30 subtidal and intertidal stations of the Bay of Brest (Brittany, France), during the winters of 2013 and 2015. Cell germinations and rDNA amplifications of A. minutum were obtained for sediments of all sampled stations, demonstrating that the whole bay is currently contaminated by this toxic species. Coherent estimations of ITS1rDNA copy numbers were obtained for the two sampling cruises, supporting the hypothesis of regular accumulation of A. minutum resting stages in the south-eastern, more confined embayments of the study area, where fine-muddy sediments are also more abundant. Higher ITS1rDNA copy numbers were detected in sediments of areas where blooms have been seasonally detected since 2012. This result suggests that specific genetic material estimations in superficial sediments of the bay may be a proxy of the cyst banks of A. minutum. The simulation of particle trajectory analyses by a Lagrangian physical model showed that blooms occurring in the south-eastern part of the bay are disconnected from those of the north-eastern zone. The heterogeneous distribution of A. minutum inferred from both water and sediment suggests the existence of potential barriers for the dispersal of this species in the Bay of Brest and encourages finer analyses at the population level for this species within semi-enclosed coastal ecosystems.     

Diversity and indicator species as measures of water pollution in a subarctic lake

Benthic invertebrates were collected from a subarctic lake during 1976 to assess the effectiveness of diversity indices and indicator species as measures of heavy metal pollution. Collections were made near an operating metal mine, where sediments were contaminated with high levels of arsenic (up to 2,500 mg/kg dry weight), mercury (500 µg/kg), lead (850 mg/kg), copper (750 mg/kg) and zinc (950 mg/kg). A total of 25 species and a diversity index of 2.4—2.9 were recorded in this heavily impacted area. Chironomids (Procladius denticulatus, Heterotrissocladius changi, Chironomus decorus) were most common in the sediments, followed in importance by molluscs (Pisidium casertanum) and oligochaetes (Lumbriculus variegatus). There were 23 and 25 species in the areas of moderate and negligible contamination, respectively. The diversity indices ranged from 2.4–2.6 and 2.4–2.8 and the main species were generally similar to those found in the heavily impacted area. While diversity indices and indicator species were therefore ineffective in monitoring metal contamination, the strong negative correlation between the concentration of metals and the abundance of benthic organisms provided a much more realistic assessment of the level of contamination.     

Mercury Contamination and Dynamics in the Sediment of the Second Songhua River,China

The Second Songhua River (SSR) was subjected to a large amount of mercury discharge from petrochemical industries in Jilin City from the 1960s to 1980s. The objectives of this study were to investigate the spatial and temporal change of mercury concentration in the sediments of the river and to assess Hg pollution in sediment employing enrichment ratio. Bottom sediments sampled in 2005 were digested with various acids followed by analysis by atomic fluorescence spectrometry for Hg, ICP-MS for Cd, Pb and Sc, and ICP-OES for Co, Cr, Cu, Zn, Mn, Ni, P, Pb, Sb, Ti, V, Al, Fe, Mg, Ca, Na, and K, in order to measure the total concentrations of these elements in the sediments. Results indicated that mercury concentrations in the sediments were strongly related with distance from the historic industrial point source, decreasing at an exponential rate from 1.27 mg kg^?1 at Jilin City to 0.01 mg kg^?1 at downstream Haerbin City. In addition, mercury concentration decreased from 16.8 mg kg^{? 1} y^?1 in 1974 to 0.09 mg kg^?1 y^?1 in 2005 in the sediments at effluent discharge site, and from 0.006 mg kg^?1 y^?1in 1974 to 0.004 mg kg^?1 y^?1 in 2005 at Songyuan City 257 km downstream. In the sedimentary sections of the river, deeper sediments contained higher concentrations of mercury as compared to the surface sediments, suggesting discharges of higher levels of mercury in the past and its subsequent burial over the years by less polluted sediments. Background concentrations of mercury in the surface sediments, reconstructed by tracer Sc, were 0.011 to 0.018 mg kg^?1. Enrichment ratios of Hg in the sediments of SSR was 5 to 75, indicating moderate to extreme pollution, while the sediment of Songhua River is less contaminated, with enrichment ratios of 0.9 to 1.5. At present, the previously accumulated and buried mercury in sediments may not significantly affect water quality of the SSR, but might pose a potential ecological risk to aquatic and amphibian animals. Natural attenuation seems to be an economic remedial choice for these sediments.     

Distribution and Contamination Status of Trace Metals in the Mediterranean Coastal Sediments,Egypt

Trace metals concentrations in sediments from the Egyptian Mediterranean coast were determined to evaluate the levels of contamination. The highest concentrations of metals were generally found in the middle region of the coast. Sediment pollution assessment was carried out using Enrichment Factor (EF), Geoaccumulation Factor (Igeo), Contamination Factor (CF), Modified Degree of Contamination (mCd), and Pollution Load Index (PLI). Association of adverse effects to aquatic life was determined using the classification of sediments according to three sets of sediment quality guidelines. The mean EF values were found to fall in the following sequence: Cr > Pb > Ni > Zn > Cu > Mn. The results demonstrated that the EF of metals in the sediments of the middle region was lower than those recorded in the western region and Rafah Station at the eastern region; the difference in the EF levels was significantly correlated with Fe concentrations along the study area. Based on the average Igeo of target elements, the Egyptian Mediterranean coast could be considered not polluted with Cr, Cu, Mn, Ni, Pb, and Zn (Igeo ≤ 0). The modified degree of contamination was >1.5, indicating zero to very low contamination. The calculated PLI were less than 1, indicating only baseline levels of pollution. There were small differences between the results obtained with the three used SQGs. Highly significant correlations were found between the concentrations of Fe, Mn, Co, Cr, and Ni, suggesting similar sources and/or similar geochemical processes controlling the occurrence of these metals in the sediments.     

COMPARISON OF HEAVY METALS IN AQUATIC PLANTS ON CHARITY ISLAND,SAGINAW BAY,LAKE HURON,U.S.A., WITH PLANTS ALONG THE SHORELINE OF SAGINAW BAY

The concentrations of 15 heavy metals in aquatic plants on Charity Island was compared to those in plants on the shoreline of Saginaw Bay, Lake Huron, U.S.A. Heavy metal concentrations were measured by neutron activation analysis. Charity Island was found to have significantly higher levels of nine of fifteen metals investigated. This indicates that distance from known pollution source was not the only factor affecting the heavy metal accumulation of the aquatic plants.     

水生昆虫对汞的吸收、富集和水-陆转移

汞是一种人体非必需且有毒的重金属元素,全球性的汞污染因对人类健康具有损害而备受社会关注。自然界中的汞绝大部分会通过江河径流和雨雪尘土的沉降而进入水生生态系统,每年进入水生生态系统的汞至少有10 000吨。水生昆虫作为重要的消费者生物存在于水生生态食物网中,是其重要的组成部分,在水生生态系统的物质循环中扮演着重要角色。本文介绍了近年来水生昆虫与汞之间的相关研究,重点总结了水生昆虫对汞的吸收和富集程度,分析了水生昆虫在汞的水-陆转移中的作用。研究数据表明,水生昆虫对汞的吸收程度与环境因素有关,并通过不同的途径转移到陆地生态系统中,对陆地生态系统上层食物链的生物存在一定的威胁,同时也需注意在对水生昆虫进行开发利用的同时,考虑汞是否超标的因素。     

微生物厌氧呼吸与有机污染水体沉积物修复

水体沉积物有机污染是当前全球关注的重要环境问题。微生物具有呼吸和代谢多样性,能以多种污染物作为厌氧呼吸的电子供体或受体,与周围环境中的生物和非生物因素组成代谢网络耦合有机污染物降解转化,是有机污染水体沉积物修复的重要驱动者。本文重点综述了微生物厌氧呼吸、电子传递网络及其对有机污染水体沉积物的修复机制研究进展,并对有机污染水体沉积物微生物修复理论和技术研究的问题和挑战进行了探讨。     

三疣梭子蟹增养殖过程对野生种群的遗传影响——以海州湾为例

为探明三疣梭子蟹人工增殖与养殖活动对野生资源的遗传影响,本文利用20对SSR引物对海州湾三疣梭子蟹野生群体与两个养殖群体进行群体遗传结构和遗传分化研究。结果表明,野生种群遗传多样性明显高于养殖群体,其群体杂合度Ho为0.8509,而两个养殖群体的杂合度Ho分别为0.4525和0.5283。海州湾野生三疣梭子蟹的 Ne、Ho、He、PIC均显著高于两个养殖群体（P<0.05）但两养殖群体的 Ne、Ho、He、PIC均无显著差异（P>0.05）。以上结果说明海州湾天然三疣梭子蟹群体的遗传多样性显著高于养殖群体。三群体间遗传分化处于中度水平（Fst,0.1085~0.1448）,基因流Nm处于1.5-2.0间,野生群体与养殖群体的遗传分化比养殖群体内部之间大,基因流也较养殖群体内部之间要小,表明野生群体与养殖群体存在一定的分化,基因流处于中等程度。因此,当前海州湾天然三疣梭子蟹遗传状况良好,养殖活动和人工增殖放流对天然资源的遗传影响还很有限,这可能与海州湾人工养殖三疣梭子蟹时间较短、人工放流的规模较小、时间较短有关。     

Assessment of the state of ovaries of some fish species from Peter the Great Bay of the Sea of Japan in relation to its anthropogenic pollution

Ovaries of four flatfish species—Liopsetta pinnifasciata, Pleuronectes obscurus, Pleuronectes yokohamae, and Glyptocephalus stelleri, as well as of Far Eastern navaga Eleginus gracilis and rudd Tribolodon brandtii caught in Peter the Great Bay of the Sea of Japan in prespawning and/or spawning periods were studied. Under conditions of anthropogenic pollution of the bay, the state of fish ovaries is determined by several factors, such as migration activity, mode of life (bottom or pelagic), and the degree of sites pollution where females stayed in the period of the vitellogenous growth of oocytes. The pollution of the bay exerts the most damaging effect on the reproductive system of shallow species of flatfish—L. pinnifasciata and P. obscurus—that do not perform far migrations and throughout their life stay in the zone exposed to toxicants. In navaga Eleginus gracilis and flatfish P. yokohamae, and G. stelleri that perform seasonal migrations, no damages of ovaries were found.     

Lo Sviluppo Del Sistema Conduttore Nelle Plantule Di “Opuntia Vulgaris„ Mill.

Aquatic mosses and sediments were monitored along Topolnitsa River Basin (Bulgaria), copper-producing and mining region. Six mosses were applied as biomonitors: Bryum turbinatum, Fontinalis antipyretica, Leptodictyum riparium, Platyhypnidium riparioides, Rhizomnium punctatum and Sciuro-hypnum plumosum. Background levels were determined for both plants and fine fraction of sediments collected from an unpolluted site. Contamination factors (CFs) and metal pollution index at each site were presented. The highest sediment enrichment with toxic elements was found in Zlatishka River. Strong increase above background levels showed all 13 heavy metals and toxic elements in biomonitors from stations at Zlatishka and Pirdopska rivers. The two moss species adopted as biomonitors for the first time – Bryum turbinatum and Rhizomnium punctatum – showed high CFs for several heavy metals and contributed to chemical pollution pattern assessment. The parallel use of mosses and sediments in the monitoring study, as well as the applied statistical tools, led to the conclusion that mosses as higher plants revealed pollution patterns not detected by sediments. Results also showed that in a seriously contaminated aquatic environment, which requires rapid assessment, different moss species can be applied for water-monitoring purposes to present preliminary picture of pollution patterns and to direct further studies.     

Environmental hazard assessment of coal ash disposal at the proposed Rampal power plant

A proposed coal-fired power plant at Rampal, Bangladesh will produce over 38 million tons of ash during 60 years of operation at 90% electric load generation capacity. The ash disposal pond would be full in twelve years even if half of all fly ash is used in concrete and brick production, leaving at least 20 million tons of ash with a disposal plan that is limited to surface impoundment and unlined fills, which are known to cause groundwater and surface water pollution. At Rampal, probable storm tides of 7.4 meters would breach the ash pond walls during the operational life of the coal plant, potentially resulting in catastrophic failure and massive spills of ash. Seasonal monsoon flooding would cause the ash pond itself to overflow, releasing huge volumes of contaminated water. Ash disposal for the proposed coal-fired power plant at Rampal, Bangladesh, would release toxic heavy metals into the waterways of the Sundarbans Delta and Bay of Bengal, which is a World Heritage Site and includes globally important mangroves, endangered aquatic species, and a fishery that feeds hundreds of thousands of poor people. The economic damage cost of the Rampal Plant could exceed $US 100 million dollars per year.